corrugated fiberboard design

Design of Corrugated Fiberboard Boxes - by tech team (JR Packages)

Historical perspective Corrugated BoardCorrugated Board Properties and TestsProperties and Tests Corrugated BoxesCorrugated Boxes Carrier RulesCarrier Rules Stacking and CompressionStacking and Compression

一 . Historical perspective

1. Appearance of corrugated paper and the development First patents for making were recorded in England in 1856. First patents in US were granted to A.L.Jones in 1871 Unlined corrugated sheet---packing lamp chimneys and fragile objects. The first user double-lined corrugated boxes was a cereal manufacturer

(obtained acceptance in 1903) Figures reversed from 20% to 80% between the world War I and II

2. The specialized produce Sheet plants buy combined board only printing and cutting. About 2000 plants produce more than 3 billion worth in India

3. Rules for constructing corrugated containers To enhance the quality Rule of UFC and NMFC

二 . Corrugated BoardCorrugated Board

1. Construction : linerboard and medium Material :heavy paper ---containerboard Facings---kraft linerboard Medium---one-ply sheet, hardwood or recycled fiber

Linerboard (flat facing)

Medium (fluted wavy)


2 Four types combined board

b. Single Wall (Double Face)

one medium two liner boards

a. Single Face

one medium one liner board (for protective wrapping)


c. Double Walltwo mediums

three liner boards

d. Triple Wall three mediums

four liner boards

Direction: Machine Direction Cross Direction ----flute direction

动画


3. Flutes Profile: arches with proper curve---- the strongest way to span space Flutes as arches--- resist bending and pressure, support weight, as cushion. Proper curve: between U and V (Also has its advantages) Flutes also as a insulator to protect sudden temperature changes Vertical linerboard provides strength; protects from damage.

Several standard shapes (A,B,C,E,F…) ,

Contrast:A-flute ---- the largest profileB-flute ----smaller than AC-flute ----between A and BE-flute ---- smaller than B F-flute ---- micro-flute New flute---Macro-flute


Combined board ---Different flute profiles combined in one board one layer of medium might be A-flute while the other C-fluteManipulate the compression and cushioning strength, total thickness of the board.

Standard flute configurations

Flute Flutes/ m Flutes/ ft Thickness * Factor

A 100~120 30~36 4.67 mm 1.54

B 145~165 44~50 2.46 mm 1.32

C 120~140 36~42 3.63 mm 1.42

E 280~310 86~94 1.19 mm 1.27

*Not including facings; 1foot = 0.3047999m “Take-up factor” is the length of medium per length of finished corrugated board

Described: the component of grammage or basis weight, from outside to inside eg. corrugated board “205/127C/161”----Outside liner = 205grams; Medium = 127 grams, formed to C-flute; Inside liner = 161grams


4 . Fiberboard Grades : Weight ; Thickness ; Material

Grammage: the mass in grams per square meter.

Basis weight: the weight in pounds per 1,000 square feet ( abbreviated lb/MSF).

The most commonly used corrugating medium weights

Grammage/g Basis Weight/b

127 26

147 30

161 33

195 40 Meterial :• Linerboard --- natural kraft ;Solid bleached white kraft ; Mottled white ; Oyserboard Linerboard with a whiter surface provide better graphics. • Recycled or secondary fiber ---producing both two components Recycled board ---smoother surface finish ;low CoF; excellent printing surface.


The most commonly used linerboard grades, based on Mullen burst test grading.

North American Grades European Grades Grammage Basis Weight Grammage 127g 26b 125g 161g 33b 150g 186g 38b -- 205g 42b 200g -- -- 225g -- -- 250g 337g 69b 300g Other grades -- 400g

-- -- 440g

1 kg = 2.2046 b

1 meter = 3.28084 foot

1 g/m2 = 0.205 b/MSF

A generation of newer linerboards has high-performance boards, meeting ECT rather than Mullen burst test and basis weight requirements.

lighter grades of the high-performance boards to get satisfactory performance


5. Corrugating Adhesive

The corrugating machine forms the medium into a fluted pattern and bonds it to the linerboard facings , usually with a starch-based adhesive1) A starch-based adhesive applied at about 10 to 14 grams per square meter.2) Requirements : not tolerant high moisture and loses strength quickly.3) When higher resistance is needed, starches can be modified or supplemented by the addition of various polymeric materials. 4) Weather-resistant adhesive would maintain box properties at a somewhat higher level for a longer period. 5) Water-resistant adhesive would be required for those applications where the finished container will be in actual contact with water for periods of time, and the coating or waxed should be treated


6. Broad ManufactureCorrugating machine is made up of a set of stations that take the appropriate linerboards and mediums, shape the flutes, join fluted medium to linerboards.

Precondition medium with heat and steam

Pretreated linerboards to the same temperature and moisture

Brass fingers

Flute tips adhesiveThe single-facer of a corrugating machine is where the flutes are formed and bonded to the inside liner


Bridge ---Draped in an overlapping wave pattern to the double-backer station Purpose---Isolating the two ends of the corrugating machine; balance; slow down

The double-backer section of corrugating machine where a second linerboard is applied to the single-faced material coming from the single-facer unit


Manufacture: Adhesive --- On the other side of the medium to glue outer linerboard. Final heating and cooling section --- Between two long , flat belts. Trimming edges--- Slit board to required width and length and stack Balanced construction--- Outer and inner have identical grammage. Upgrading only one liner may gain performance. Unbalanced constructions --- more problems with board wrappage. Heavier liner is placed on the outside for better printing and on the insi

de for better compression strength.

三 . Properties and TestsProperties and Tests

Most board tests are described in methods provided by TAPPI.

Standard corrugated board burst and crush tests.

1. Mullen burst test (TAPPI T 810) Forcing a rubber diaphragm against the facing until it bursts


2. ECT (TAPPI T 811) A small specimen is placed between the platens of a compression

tester and loaded until failure occurs. Values are a function of the stiffness contributed by the facings and the medium. ECT values have a direct relationship to the projected stacking strength.

3. Flat Crush Test (TAPPI T 808) Similar to the edge compression test except the specimen is

compressed in the flat. The test provides a measure of flute rigidity.4. Combined Weight of Facings Describes the combined linerboard weight per 1,000 square feet of

corrugated board5. Thickness of Corrugated Board (TAPPI T 411) Reduced board thickness (caliper) is an excellent indicator of reduced

compression strength; Caliper can be reduced by improper manufacture, excessive printing pressure, improper handling and storage


6. Gurley Porosity (TAPPI T 460 and T 536)

Measures the time it takes for a given volume of air to pass through a paper. The lower the number, the more porous the paper. The porosity of paper is sometimes the culprit when problems occur at vacuum-cup transfer points.

7. Flexural Stiffness (TAPPI T 820) Rrelated to box compression strength. Reduced stiffness is a good indica

tor of damage during fabrication. 8. Water Take-up Tests (TAPPI T 441) The Cobb size test, measures the amount of water absorbed by the facing

in a given time, used to measure water absorption for materials specified to be used for hazardous product containers


9. Puncture Test (TAPPI T 803) Measures the energy required to puncture a board with a triangular pyra

midal point affixed to a pendulum arm. Test the resistance and stiffness of triple wall corrugated The box maker’s stamp on triple wall containers calls for a puncture tes

t10. Pin Adhesion (TAPPI T 821) P

in adhesion quantifies the strength of the bond between the medium's flute tips and the linerboard facings.

11. Ply Separation (TAPPI T 812) Evaluates the board's resistance to ply separation when exposed to wate

r. 12. Coefficient of Friction (TAPPI T 815 and ASTM 04521). CoF can affect machinability and load stability. A stress/strain machine

method will give both static and dynamic CoF values

四四 . Corrugated Boxes. Corrugated Boxes

1. 1. Selecting the Correct Flute

use a carrier classification and C-flute as good starting points.

Characteristic A-Flute* B-Flute C-Flute E-Flute

Stack strength best* fair good poor

Printing poor good fair best

Die cutting poor good fair best

Puncture good fair best poor

Storage space most good fair least

Score/bend poor good fair best

Cushioning best fair good poor

Flat crush poor good fair fair

Comparison of corrugated board characteristics


E- and F-flutes are not used in shipping containers but rather are replacements for thicker grades of solid paperboard. Can be considered if a folding carton design calls for boards thicker than 750(30 point). Also be used to replace paperboard for heavier or special protective primary packs as primary container while in distribution. Such as small tools, hardware, small appliances, and housewares…

A-flute originally specified, not commonly use . almost 5 mm (1/4 in.) Occupies more space ,has significantly greater deflection before bearing a load when compressed. The thicker section give it the highest top-to-bottom compression strength. A-flute has the lowest flat crush resistance

B-flute is used where box stacking strength is not required. B-flute's has high flat crush strength when supporting heavy goods.

C-flute --- 10% better stacking strength than the same weights of B-flute


Medium Grammage A- Flute C- Flute B- Flute

127g 0.70 1.00 1.15

161g 0.90 1.25 1.45

195g 1.10 1.50 N.A

Relative flute flat crush values


2. Box 2. Box Style Many standard box styles can be identified in three ways: by a descriptive name,

by an acronym based on that name, or by an international code number. For example, a Regular Slotted Container could also be referred to as an RSC or as #0201.

There are many standard corrugated box styles: Slotted Boxes, Telescope Boxes, Folders, Rigid Boxes (Bliss Boxes), Self-Erecting Boxes and Interior Forms

“Regular Slotted Container”(RSC or #0201) is the workhorse corrugated box style (Figure 4.10). All his flaps have the same length, and the two outer flaps (normally the lengthwise flaps) are one-half the container's width, so that they meet at the center of the box when folded. If the product requires a flat, even bottom surface, or the protection of two full layers, a fill-in pad can be placed between the two inner flaps.


Figure 4.10 Parts of a regular slotted container (RSC) blank


3. Manufacturer's joint A flat piece of corrugated fiberboard, which has been cut, slotted and

scored, is called box blank. For some box styles, in order to make a box, the two ends of the box blank must be fastened together with tape, staples or glue. The place where these two ends meet is known as the manufacturer's joint.

Liquid adhesives are most often used to join the two surfaces. Often there is a glue tab, extending along one end of the box blank. The tab can be joined to either the inside or the outside of the box. If there is no tab, the box must be joined using tape. Not all boxes have manufacturers joints; for example, the bliss box does not.


Bliss style container Bliss-style box design variations

4. Dimensioning Dimensions are given in the sequence of length, width and depth. Dimensions can be specified for either the inside or the outside of the box. Accurate inside dimensions must be determined to ensure the proper fit for the product being shipped or stored. At the same time, palletizing and distributing the boxes depends on the outside dimensions. The box manufacturer should be informed as to which


Top Loading End Loading

五五 . Carrier Rules. Carrier Rules

1. Application The Uniform Freight Classification (UFC) and National Motor

Freight Classification (NMFC) were established to categorize articles for shipment via common carrier with respect to value, density, fragility, and potential for damage to other freight.

The classifications specify the conditions under which specific articles can be shipped and at what rates. When shipping by rail, refer to UFC. When shipping by truck, refer to NMFC. UFC rule 41 and NMFC item 222 are the most frequently used in describing corrugated packaging.

There are four basic steps for determining authorized packaging: 1. Fully identify the product. 2. Select the proper governing classification. 3. Use the "Index to Articles" to find the applicable item number. 4. Consult the proper article to find the required packaging.


Failure to comply with regulations can subject the shipper to penalties such as higher freight rates, refusal of acceptance by the carrier, or nonpayment of damage claims.

2. Summary of Rules for Corrugated Box Construction Carrier rules for corrugated box construction can be summarized as

follows: Specified boards (using either Mullen burst test or ECT values) shall

be used for a given product weight, providing the box does not exceed a specified dimensional limit. The dimensional size limit for a box is determined by adding an outside length, width, and depth.

Table 4.6 summarizes the construction requirements for corrugated boxes. The rules also require that a box manufacturer’s certificate (BMC) on the bottom of the container ( Figure 4.11).


Figure 4.11 Box manufacturer's certificates using burst test and ECT values


PART A* PART B*

Maximum weight of Box and Contents(lb

s.)

Maximum Outside Dimension, Length, Width and Depth Adde

d(in.)

Minimum Burst Test, Single Wall, Double Wall

or Solid Fiberboard(lbs.per sq.in.)

orMinimum Puncture Test, Triple Wall Board(in.oz.

per in.of tear)

Minimum Combined Weight of Facings,including Center Facing(s) of Double Wall and Triple

Wall Boardor

Minimum Combined Weight of Pliers, Solid Fiberboard, Excluding Adhesives(lbs.per 1,000 sq.

ft.)

Minimum Edge Crush Test

(ECT)(lbs. per in.

width)

Table 4.6 Summary of carrier rules for corrugated boxes


Single Wall Corrugated Fiberboard Boxes

203550658095

120

405060758595

105

125150175200250275350

52667584

111138180

23262932404455

Double Wall Corrugated Fiberboard Boxes

80100120140160180

8595

105110115120

200275350400500600

92110126180222270

424851617182


Triple Wall Corrugated Fiberboard Boxes

240260280300

110115120125

700900

11001300

168222264360

678090

112

Solid Fiberboard Boxes

20406590

120

40607590

100

125175200275350

114149190237283

* Mullen(Part A) and ECT(Part B) are presented side-by-side, but there is no correlation between the values

六六 . Stacking and Compression. Stacking and Compression

1. McKee formula Stacking strength is defined as the maximum compressive load (pounds

or kilograms) that a container can bear over a given length of time, under given environmental/ distribution conditions without failing.

The ability to carry a top load is affected by the structure of the container and the environment it encounters, and the ability of the inner (primary) packages and the dividers, corner posts, etc. to sustain the load.

The simplest and most common corrugated transport packages are regular slotted containers (RSCs, Box Style 0201) in which the corrugation direction is typically vertical-parallel to top- bottom stacking forces.

Compression strength of regular slotted containers is a function of: ·Perimeter of the box (two times length plus two times width) ·Edge crush test of the combined board ·Bending resistance of the combined board ·Aspect ratio (L:W) and other factors


When we know the above variables, we can estimate the compression strength through an equation known as the McKee formula.

BCT=2.028× (ECT)0.746× ((Dx×Dy)0.254)1/2 ×BP0.492 (4.1)

Where: BCT = RSC top-to-bottom box compression strength, kN/m2(lbf/in.2 or p.s.i) ECT = edge crush test, kN/m (lbf/in.) Dx,Dy = flexural stiffnesses of combined board in the machine direction and cross direction, kN/m(lbf/in.) BP = inside box perimeter, m (in.)


The McKee formula can only be applied to RSCs, and only those with a perimeter-to-depth ratio no greater than 7:1.

McKee also created a simpler formula based on caliper of the combined board instead of bending stiffness:

BCT=5.87×ECT× (T×BP)1/2 (4.2) Where: T = caliper of combined board, m (in.) Solving for ECT, the simplified McKee formula is: ECT = BCT /[5.87× (T ×BP)1/2] (4.3）


The ability of a container to perform in distribution is significantly impacted by the conditions it encounters throughout the cycle.

If the original box compression strength is known, we can factor it by generally accepted multipliers to arrive at an estimated maximum safe stacking strength (Table 4.7)

2. Distribution Environment and Container Performance

Compression Loss Multifliers

Storage time under load

10 days-37 percent loss 0.63




Relative humidity, under load(cyclical RH variation further increase c

ompressive loss)

50 days-0 percent loss 1






Table 4.7 Environmental Stacking Factors

Pallet Patterns Best Case Worst Case

Columnar, aligned Negligible loss

Columnar, misaligned 10-15 percent loss 0.9 0.85

Interlocked 40-60 percent loss 0.6 0.4

Overhang 20-40 percent loss 0.8 0.6

Overhang 10-25 percent loss 0.9 0.75

Excessive handling 10-40 percent loss 0.9 0.6


3. Compression Requirement If the compression strength and distribution environment is known, the effective stacking strength of any given RSC can be reasonably estimated. If the distribution environment, container dimensions and flute profile are known, a compression requirement can be estimated. This can be of great value, because once a compression requirement is determined, the ECT requirement can be determined (and, therefore, board combination options as well). [Example] A box of 0.5 m × 0.25 m× 0.30 m （ outside dimensions） will have 12 kg, stacked 3 m high in the warehouse. Boxes will be arranged in an interlock pattern and will be required to hold the load for 180 days at 80% R.H.. The pallets are in good condition; there will be no overhang. What should the required compression strength of the box be ?


1). Determine maximum number of boxes above bottom box: 3 /0.30 -1= 8

2). Determine load on bottom box: 8×12 kg = 96 kg 3). Determine Environmental Factor by multiplying together all factors th

at apply: 180 days, 0.50 80% R.H. 0.68 Interlocked stack 0.50 Multiplier product(Environmental Stacking Factors) 0.17 4). Determine required box compression strength: BCT = anticipated load/stacking factor=96 kg/0.17=564 kg Now that the actual compression strength is know, this value can be plug

ged into the McKee formula (4.3), and the required edge crush test (ECT) value of the corrugated board can be calculated.


4. Compression Solutions Following are a variety of approaches to increase compression and stac

king strength. The most efficient and cost-effective approach will depend on the product, package size and distribution environment.

·Stronger liners and medium(s) ·Load sharing ·Increase the number of corners ·Change corrugation direction ·Dimensions: Depth, Length to width, Perimeter, Panel size ·Multiwall corrugated fiberboard ·Partitions, inserts and interior packaging ·Lamination ·Treatments, impregnations and coatings

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